Subject of the invention is an elevator installation.
Elevator installations of the kind according to the invention usually comprise an elevator cage and a counterweight, which are movable in an elevator shaft or along free-standing guide devices. For producing the movement the elevator installation comprises at least one drive with at least one respective drive pulley, which, by way of support means and/or drive means, support the elevator cage and the counterweight and transmit the required drive forces to these.
In the following, for the sake of simplicity the support means and/or drive means are termed only support means.
An elevator system without an engine room is known from WO 03/043926, in which wedge ribbed belts are used as support means for the elevator cage. These belts comprise a belt body of flat belt form which is produced from a resilient material (rubber, elastomer) and which has, on its running surface facing the drive pulley, several ribs extending in the belt longitudinal direction. These ribs co-operate with grooves, which are formed to be complementary thereto, in the periphery of driving or deflecting pulleys (termed belt pulleys in the following) in order on the one hand to guide the wedge ribbed belt on the drive pulleys and on the other hand to increase the traction capability between the drive pulley and the support means. The ribs and grooves have triangular or trapezium-shaped, i.e. wedge-shaped, cross-sections. Tensile carriers consisting of metallic or non-metallic strands are embedded in the belt body of the wedge ribbed belt and oriented in the belt longitudinal direction, which tensile carriers impart the requisite tensile strength and longitudinal stiffness to the support means.
The wedge-ribbed belts known from WO 03/043926 have certain disadvantages, i.e. they are not optimally adapted to the requirements of a support means for elevator cages. Such support means have to have a high load-bearing capability and a low longitudinal elasticity for smallest possible dimensions and smallest possible own weight and in that case be able to be guided over driving and deflecting pulleys with smallest possible diameters.
The wedge ribbed belts used as support means in accordance with WO 03/043926 exhibit, by comparison with the cross-sections of the tensile carriers, relatively large cross-sections of the belt bodies, i.e. the thickness of the belt bodies is large in relation to the diameter of the tensile carriers, and the edge regions, which face the pulleys and rollers, of the belt bodies, particularly the tips of the wedge-shaped ribs, are spaced comparatively far from the tensile carriers. In the case of the cross-section, which is given by the required load-bearing strength, of the tensile carriers this means that the disclosed wedge ribbed belts on the one hand have more than the absolutely necessary amount of material for the belt body and thus are too heavy and too expensive. On the other hand, the material of the belt body, which is relatively high in bending direction, is needlessly strongly loaded by alternating bending stresses when the support means runs around a drive pulley or a deflecting roller of small diameter, which can lead to formation of cracks and premature failure of the support means. In particular, the regions of the belt body spaced far from the tensile carriers, i.e. the tips of the wedge-shaped ribs, are exposed to strong alternating bending stresses.